The concept of inevitable premalignancy in all adenomatous polyps of the colon was challenged as early as 1958, and since that time much debate has centered about the malignant potential of adenomatous polyps of the colon. Current thinking indicates that the majority of colonic polyps fall into one of four categories: hyperplastic, villous adenoma, adenomatous, and villoglandular. Analysis of the present series of 387 colonic polyps removed endoscopically indicates that the villoglandular group has a notable malignant potential, and that the pure adenomatous polyp probably carries a minimal malignant threat. The present series does not challenge the accepted concept that hyperplastic polyps are of no malignant potential, and that villous adenomas are quite frequently malignant at the time of diagnosis.